6L5-14301-1 Thermostat for Yamaha 3HP 3M 3A AMHL MSH AMHS AMH MSHA MSHB | JLM Marine

Thermostat for Yamaha 3HP Outboard Engines – Fits 3M, 3A, AMHL, MSH, AMHS, AMH, MSHA, MSHB

This high-quality aftermarket thermostat is designed to fit Yamaha 3HP outboard engines across multiple model designations, including 3M (1990–2002), 3A, AMHL, and MSH (1988–1999), 3A, AMHS, AMHL, AMH, MSHA, and MSHB (2001–2010), and AMH, AMHS (2011–2015). Engineered to maintain optimal engine temperature and protect against overheating, this thermostat ensures reliable performance season after season.

This part directly replaces Yamaha OEM part numbers 6L5-14301-1, 6L5-14301-02-00, 6L5-14301-03-00, 6L5143010300, 6L5-14301-03, and 6L5-14301-01, providing broad compatibility across nearly three decades of Yamaha 3HP models.

• Precision-engineered to OEM specifications for consistent thermal regulation
• Direct bolt-on replacement—no modifications required
• Compatible with Yamaha 3HP engines from 1988 to 2015

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket references.

Compatible Engine Models

Confirm your engine model/year in the table below. For Yamaha owners, here's a guide to help you identify your engine's serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 × Thermostat (Yamaha OEM# 6L5-14301-1)

Installation Guide

1. Disconnect the fuel line and allow the engine to cool completely before beginning work.
2. Remove the engine cowling to access the thermostat housing, typically located near the cylinder head.
3. Drain or contain coolant as needed to prevent spills; note the orientation of hoses and fittings.
4. Unscrew or unclip the thermostat housing cover and carefully remove the old thermostat.
5. Clean the mating surfaces of the housing and cover, removing any old gasket material or debris.
6. Position the new thermostat in the housing, ensuring the temperature-sensing element faces the correct direction (check your service manual if unsure).
7. Install a new gasket or O-ring if provided, then reattach the housing cover and torque fasteners to specification.
8. Reconnect all hoses and refill the cooling system with fresh water or coolant as per your engine's requirements.
9. Start the engine and monitor for leaks around the thermostat housing during the first few minutes of operation.
10. Allow the engine to reach normal operating temperature and verify that the thermostat opens correctly (check for proper water flow from the tell-tale).

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my Yamaha 3HP engine?
A: Cross-reference your engine's model designation (3M, 3A, AMHL, MSH, AMHS, AMH, MSHA, or MSHB) and year (1988–2015) with the compatibility table above. You can also verify your original part number matches 6L5-14301-1 or any of its superseded versions listed.

Q: What are the signs that my thermostat needs replacement?
A: Common symptoms include engine overheating, inconsistent temperature readings, reduced water flow from the tell-tale, or the engine running too cool (poor fuel economy and sluggish performance). If you notice any of these issues, inspect and test your thermostat.

Q: How often should I replace the thermostat on my Yamaha 3HP outboard?
A: Yamaha recommends inspecting the thermostat annually and replacing it every 2–3 years or sooner if you experience overheating or cooling system problems. Saltwater environments may require more frequent replacement due to corrosion.

Q: Can I install this thermostat myself, or do I need a professional?
A: If you have basic mechanical skills and follow the service manual, DIY installation is straightforward. However, professional installation is recommended to ensure proper torque settings, gasket sealing, and system refilling.

Q: Is this an OEM Yamaha thermostat or an aftermarket part?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.